The present invention relates to a capsule chemistry sample liquid analysis system adapted for the automated clinical analysis of pluralities of human biological sample liquids, in particular to a method and apparatus for conducting a stat immunoassay analysis in such a system.
U.S. Pat. Nos. 5,268,147 (the xe2x80x9c""147 patentxe2x80x9d) and 5,399,497 (the xe2x80x9c""497 patentxe2x80x9d), owned by the assignee hereof, the disclosures of which are incorporated herein by reference, describe a capsule chemistry sample liquid analysis system which operates through repeated reversible, bi-directional flow of an appropriately configured stream of liquid test packages, each test package consisting of alternating segments of a liquid, such as a sample, reagent or buffer, and air, to enable repeated, precisely timed analysis of the sample of each of the test packages in the stream by one or more sample liquid analysis means. As described in the ""147 and ""497 patents, the system generally comprises a sample liquid test package metering and supply means which operates to meter successive test packages for reaction and analysis within the system; a reversible direction sample liquid test package displacement means which operates to bi-directionally displace the thusly metered and supplied test packages through the system; a test package transfer means which operates in conjunction with the test package metering and supply means and the test package displacement means to provide for the successive test package supply and bi-directional functions of the system; test package reaction and analysis means for analysis of the thusly supplied and displaced text packages; and detection means operatively associated with the reaction and analysis means to detect and quantify the successive sample liquid test package analysis results.
Such a system is particularly adapted to conduct automated clinical analysis of pluralities of human biological sample liquids and can be configured to perform various specific analyses, including a well known so called immunoassay analysis. An embodiment of the system just described configured for conducting an immunoassay analysis is shown in FIG. 1.
As described in detail in the ""147 and ""497 patents, the system generally operates by creating a plurality of test packages and successively inserting the test packages into analytical line 30 shown in FIG. 1, which preferably comprises a flexible conduit made of transparent Teflon or like material. Co-pending U.S. application Ser. No. 09/111,162, owned by the assignee hereof, the disclosure of which is incorporated herein by reference, describes in detail how the apparatus shown in FIG. 1, which includes an aspirating probe 10 connected to a service loop 15, a liquid supply 20, an aspiration pump 25, a transfer loop 35, and a shear valve 40, is able to create and subsequently insert the liquid test packages into the analytical line 30 for analysis. Accordingly, that discussion will not be repeated herein.
After insertion into the analytical line 30, the test packages are repeatedly and bi-directionally flowed back and forth in the analytical line 30, through operation of the stream pump 46 shown in FIG. 1, and ultimately past the appropriate test package reaction, analysis and detection means. Depending on the type of analysis being done, particular devices are disposed along the analytical line 30 so as to comprise the reaction, analysis and detection means. As shown in FIG. 1, a configuration appropriate for conducting an immunoassay analysis includes vanish zone 50, first, second and third bubble detectors 55, first and second magnets 60 and luminometer 65. The functionality of these components is described in greater detail both below and in the ""147 and ""497 patents.
It will be apparent to one of skill in the art that a test package suitable for a so-called sandwich type magnetic particle-based heterogeneous immunoassay is as shown in FIG. 2. In particular, this test package consists of six liquid segments: a magnetic particle suspension designated as MP, a mixture of sample and first and second reagents designated as S/R1/R2, a first wash designated as W1, a second wash designated as W2, a combination of a third reagent and a fourth reagent designated as R3/R4, and a marker dye designated as D. As illustrated in FIG. 2, each of these liquid segments is separated by an air segment It will also be apparent to one of skill in the art that additional suitable immunoassay protocols, and thus additional immunoassay test packages, exist, for example a test package containing eight liquid segments. In addition, the test package shown in FIG. 2, as well as the one described below and shown in FIG. 3, could include an additional buffer liquid segment as the first liquid segment.
As will be known by one of skill in the art, in a typical sandwich immunoassay analysis which utilizes the test package shown in FIG. 2, the sample S is allowed to react with first and second reagents R1 and R2 within the test package for a particular, fixed period of time as defined by the assay protocol. Then, the magnetic particles are transferred out of the magnetic particle suspension MP and into the S/R1/R2 segment, where they are allowed to mix for an additional specified amount of time as defined by the assay protocol. Thereafter, the magnetic particles are separated from the S/R1/R2 segment, are transferred to and washed in washes W1 and W1, and are transferred to and reacted with a combination of third and fourth reagents R3/R4. The reaction between the magnetic particles and the combination of third and fourth reagents R3/R4 generates a detectable response in the form of emitted photons which are in proportion to the analyte concentration in the sample S. The R3/R4 segment which is emitting photons is commonly referred to as a glowing segment. As noted above, a suitable apparatus for carrying out such an immunoassay is shown in FIG. 1 and includes first and second magnets 60, first, second and third bubble detectors 55 and luminometer 65. The first magnet 60 is used to transfer the magnetic particles into the S/R1/R2 segment after a specific amount of time, and the second magnet 60 is used to transfer the magnetic particles from the S/R1/R2 segment into washes W1 and W2 and ultimately into the R3/R4 segment. The luminometer 65 is used to detect and measure the photons emitted from the segment R3/R4 containing the magnetic particles. Bubble detectors 55 are capable of sensing an interface between an air segment and a liquid segment in a flowing stream of air and liquid segments and thus are used to track the flow of the stream of test packages in the analytical line 30. Bubble detectors are well known in the art, examples of which are described in U.S. Pat. No. 5,466,946 and U.S. application Ser. No. 08/995,738, both owned by the assignee hereof, the disclosures of which are incorporated herein by reference.
In the sandwich immunoassay analysis just described, the time that it takes for the reactions and various washes to be completed, and thus ultimately the time that it takes to yield a glowing segment that can be analyzed, is typically relatively long, for example, on the order of twenty minutes. It may, however, often be desirable to obtain analysis results for a particular sample S in a much shorter time period. A so-called stat immunoassay, which utilizes the test package shown in FIG. 3, has been developed for providing analysis results in a quicker fashion. As can be seen by comparing FIG. 2 and FIG. 3, the conventional immunoassay test package, i.e., a non-stat immunoassay test package, and the stat immunoassay test package differ in that for the stat immunoassay, the magnetic particular suspension MP is aspirated along with the sample S, the reagent R1 and the reagent R2 when the test package is created, rather than being separated therefrom by an air segment. Thus, for a stat immunoassay, the immunochemical reactions start as soon as the test package is created, and therefore a measurement can be made much sooner after the test package has been created.
As will be apparent to one of skill in the art, in order to use such a stat immunoassay package in a system such as the one shown in FIG. 1, it would be necessary to insert additional hardware along the analytical line 30, in particular at least an additional magnet and an additional luminometer at a position relatively close to the point where the test packages are inserted into the analytical line 30. Such a configuration and use of a stat immunoassay would, however, create a significant problem. In particular, as will be apparent to one of skill in the art, if a stat immunoassay test package as shown in FIG. 3 were to be inserted into the analytical line 30 along with other conventional immunoassay test packages, there would be, for a period of time during which the stat immunoassay test package is in the analytical line 30, two glowing segments in the analytical line 30 at the same time. The presence of two glowing segments in the analytical line 30 at the same time can result in photons from one glowing segment, i.e., the stat immunoassay glowing segment, being transmitted through the analytical line 30 and scattered into the detector of the luminometer 65 that is measuring the photons being emitted by the glowing segment of a conventional immunoassay test package. This phenomenon, known as optical carryover, will in most cases cause an error in the readings taken by that luminometer 65.
According to an aspect of the present invention, an apparatus for analyzing a plurality of samples according to an analysis protocol is provided, wherein each of the samples is contained within a liquid test package comprising a plurality of liquid and air segments including a reagent segment, and wherein during at least a portion of the protocol the reagent segment emits photons. At least one of the liquid test package includes a buffer segment separated from the reagent segment by a vanish bubble. The apparatus comprises a fluid conduit through which the liquid test packages are flowed, a first luminometer positioned along the fluid conduit for detecting photons emitted by the reagent segment of the at least one of the liquid test packages, a second luminometer positioned along the fluid conduit for detecting photons emitted by the reagent segments of the liquid test packages other than the at least one of the liquid test packages, and a vanish zone contained within the fluid conduit between the first and second luminometers. The reagent segment and the buffer segment of the at least one of the liquid test packages are mixed together in the vanish zone.
According to a further aspect of the present invention, the reagent segments emit photons as a result of a light-producing reaction requiring a high pH level, the buffer segments have a low pH level, and when the buffer segments and the reagent segments are mixed in the vanish zone, the light-producing reaction substantially ceases. According to still a further aspect of the present invention, each of the liquid test packages includes a segment containing magnetic particles. The apparatus according to this aspect further comprises a magnet positioned along the fluid conduit at a location in front of the first luminometer, the magnetic being adapted to transfer the magnetic particles of the at least one of the liquid test packages between the liquid segments of the at least one of the liquid test packages. According to yet a further aspect of the present invention, the apparatus includes a bubble detector positioned along the fluid conduit at a location in front of the magnet for detecting interfaces between the liquid segments and the air segments of the liquid test packages.
According to a still further aspect of the present invention, a method of analyzing a plurality of samples according to an analysis protocol is provided, wherein each of the samples is contained within a liquid test package comprising a plurality of liquid and air segments including a reagent segment, and wherein during at least a portion of the protocol the reagent segment emits photons. At least one of the liquid test packages includes a buffer segment separated from the reagent segment by an air segment. The method comprises the steps of inserting the liquid test packages into a fluid conduit, flowing the liquid test packages past a first luminometer positioned along the fluid conduit and detecting photons emitted by the reagent segment of the at least one of the liquid test packages, mixing the reagent segment and the buffer segment of the at no least one of the liquid test packages after the photons have been detected, and flowing the liquid test packages past a second luminometer positioned along the fluid conduit and detecting photons emitted by the reagent segments of the liquid test packages other than the at least one of the liquid test packages.